使用 Objective-C 发布多部分/表单数据

确定图片的路径:

Determine the path for the image:

NSString *path = [[NSBundle mainBundle] pathForResource:@"avatar" ofType:@"png"];

创建请求:

Create the request:

NSString *boundary = [self generateBoundaryString];

// configure the request

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:@"POST"];

// set content type

NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary];
[request setValue:contentType forHTTPHeaderField: @"Content-Type"];

// create body

NSData *httpBody = [self createBodyWithBoundary:boundary parameters:params paths:@[path] fieldName:fieldName];

这是上面用来构建请求正文的方法:

This is the method used above to build the body of the request:

- (NSData *)createBodyWithBoundary:(NSString *)boundary
                        parameters:(NSDictionary *)parameters
                             paths:(NSArray *)paths
                         fieldName:(NSString *)fieldName {
    NSMutableData *httpBody = [NSMutableData data];

    // add params (all params are strings)

    [parameters enumerateKeysAndObjectsUsingBlock:^(NSString *parameterKey, NSString *parameterValue, BOOL *stop) {
        [httpBody appendData:[[NSString stringWithFormat:@"--%@
", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name="%@"

", parameterKey] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:[[NSString stringWithFormat:@"%@
", parameterValue] dataUsingEncoding:NSUTF8StringEncoding]];
    }];

    // add image data

    for (NSString *path in paths) {
        NSString *filename  = [path lastPathComponent];
        NSData   *data      = [NSData dataWithContentsOfFile:path];
        NSString *mimetype  = [self mimeTypeForPath:path];

        [httpBody appendData:[[NSString stringWithFormat:@"--%@
", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name="%@"; filename="%@"
", fieldName, filename] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:[[NSString stringWithFormat:@"Content-Type: %@

", mimetype] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:data];
        [httpBody appendData:[@"
" dataUsingEncoding:NSUTF8StringEncoding]];
    }

    [httpBody appendData:[[NSString stringWithFormat:@"--%@--
", boundary] dataUsingEncoding:NSUTF8StringEncoding]];

    return httpBody;
}

以上使用了以下实用方法:

The above uses the following utility methods:

@import MobileCoreServices;    // only needed in iOS

- (NSString *)mimeTypeForPath:(NSString *)path {
    // get a mime type for an extension using MobileCoreServices.framework

    CFStringRef extension = (__bridge CFStringRef)[path pathExtension];
    CFStringRef UTI = UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension, extension, NULL);
    assert(UTI != NULL);

    NSString *mimetype = CFBridgingRelease(UTTypeCopyPreferredTagWithClass(UTI, kUTTagClassMIMEType));
    assert(mimetype != NULL);

    CFRelease(UTI);

    return mimetype;
}

- (NSString *)generateBoundaryString {
    return [NSString stringWithFormat:@"Boundary-%@", [[NSUUID UUID] UUIDString]];
}

然后提交请求.这里有很多很多的选择.

Then submit the request. There are many, many options here.

例如，如果使用NSURLSession，你可以创建NSURLSessionUploadTask:

For example, if using NSURLSession, you could create NSURLSessionUploadTask:

NSURLSession *session = [NSURLSession sharedSession];  // use sharedSession or create your own

NSURLSessionTask *task = [session uploadTaskWithRequest:request fromData:httpBody completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    if (error) {
        NSLog(@"error = %@", error);
        return;
    }

    NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"result = %@", result);
}];
[task resume];

或者你可以创建一个NSURLSessionDataTask:

request.HTTPBody = httpBody;

NSURLSessionTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    if (error) {
        NSLog(@"error = %@", error);
        return;
    }

    NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"result = %@", result);
}];
[task resume];

以上假设服务器只是返回文本响应.如果服务器返回 JSON 会更好，在这种情况下，您将使用 NSJSONSerialization 而不是 NSString 方法 initWithData.

The above assumes that the server is just returning text response. It's better if the server returned JSON, in which case you'd use NSJSONSerialization rather than NSString method initWithData.

同样，我正在使用上面 NSURLSession 的完成块再现，但也可以随意使用更丰富的基于委托的再现.但这似乎超出了这个问题的范围，所以我将把它留给你.

Likewise, I'm using the completion block renditions of NSURLSession above, but feel free to use the richer delegate-based renditions, too. But that seems beyond the scope of this question, so I'll leave that to you.

但希望这能说明这个想法.

But hopefully this illustrates the idea.

如果我没有指出那我会失职，比上面容易得多，你可以使用 AFNetworking，重复上面的步骤 1 和 2，然后只是调用:

I'd be remiss if I didn't point that, much easier than the above, you can use AFNetworking, repeating steps 1 and 2 above, but then just calling:

AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
manager.responseSerializer = [AFHTTPResponseSerializer serializer]; // only needed if the server is not returning JSON; if web service returns JSON, remove this line
NSURLSessionTask *task = [manager POST:urlString parameters:params constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
    NSError *error;
    if (![formData appendPartWithFileURL:[NSURL fileURLWithPath:path] name:@"avatar" fileName:[path lastPathComponent] mimeType:@"image/png" error:&error]) {
        NSLog(@"error appending part: %@", error);
    }
}  progress:nil success:^(NSURLSessionTask *task, id responseObject) {
    NSLog(@"responseObject = %@", responseObject);
} failure:^(NSURLSessionTask *task, NSError *error) {
    NSLog(@"error = %@", error);
}];

if (!task) {
    NSLog(@"Creation of task failed.");
}

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